From: Xu Kuohai xukuohai@huawei.com
Add helper to read lsm hook return value range. The following patch will use this information to verify lsm hook return values in bpf verifier.
Signed-off-by: Xu Kuohai xukuohai@huawei.com --- include/linux/bpf_lsm.h | 8 ++++++ kernel/bpf/bpf_lsm.c | 54 ++++++++++++++++++++++++++++++++++++++++- 2 files changed, 61 insertions(+), 1 deletion(-)
diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 1de7ece5d36d..e51c042abf43 100644 --- a/include/linux/bpf_lsm.h +++ b/include/linux/bpf_lsm.h @@ -9,6 +9,7 @@
#include <linux/sched.h> #include <linux/bpf.h> +#include <linux/bpf_verifier.h> #include <linux/lsm_hooks.h>
#ifdef CONFIG_BPF_LSM @@ -45,6 +46,8 @@ void bpf_inode_storage_free(struct inode *inode);
void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, bpf_func_t *bpf_func);
+int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range); #else /* !CONFIG_BPF_LSM */
static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id) @@ -78,6 +81,11 @@ static inline void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog, { }
+static inline int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *range) +{ + return -EOPNOTSUPP; +} #endif /* CONFIG_BPF_LSM */
#endif /* _LINUX_BPF_LSM_H */ diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index ee9d1a795334..4e1a4a333000 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -11,7 +11,6 @@ #include <linux/lsm_hooks.h> #include <linux/bpf_lsm.h> #include <linux/kallsyms.h> -#include <linux/bpf_verifier.h> #include <net/bpf_sk_storage.h> #include <linux/bpf_local_storage.h> #include <linux/btf_ids.h> @@ -40,6 +39,29 @@ noinline RET bpf_lsm_##NAME(__VA_ARGS__) \ #undef LSM_RET_INT #undef LSM_RET_VOID
+struct lsm_retval_desc { + unsigned long func_addr; + int minval; + int maxval; +}; + +#define LSM_RET_INT(defval, min, max) min, max + +#define LSM_HOOK_RETVAL_int(NAME, ...) \ +{ (unsigned long)&bpf_lsm_##NAME, __VA_ARGS__ }, + +#define LSM_HOOK_RETVAL_void(NAME, ...) + +#define LSM_HOOK(RET, RET_DESCRIPTION, NAME, ...) \ +LSM_HOOK_RETVAL_##RET(NAME, RET_DESCRIPTION) + +static struct lsm_retval_desc lsm_retvalues[] = { +#include <linux/lsm_hook_defs.h> +}; +#undef LSM_HOOK +#undef LSM_RET_INT +#undef LSM_RET_VOID + #define LSM_HOOK(RET, DEFAULT, NAME, ...) BTF_ID(func, bpf_lsm_##NAME) BTF_SET_START(bpf_lsm_hooks) #include <linux/lsm_hook_defs.h> @@ -399,3 +421,33 @@ const struct bpf_verifier_ops lsm_verifier_ops = { .get_func_proto = bpf_lsm_func_proto, .is_valid_access = btf_ctx_access, }; + +static struct lsm_retval_desc *find_retval_desc(const char *func_name) +{ + unsigned long addr; + struct lsm_retval_desc *desc; + + addr = kallsyms_lookup_name(func_name); + for (unsigned int i = 0U; i < ARRAY_SIZE(lsm_retvalues); i++) { + desc = &lsm_retvalues[i]; + if (addr == desc->func_addr) + return desc; + } + + return NULL; +} + +int bpf_lsm_get_retval_range(const struct bpf_prog *prog, + struct bpf_retval_range *retval_range) +{ + struct lsm_retval_desc *desc; + + desc = find_retval_desc(prog->aux->attach_func_name); + if (desc == NULL) + return -ENODEV; + + retval_range->minval = desc->minval; + retval_range->maxval = desc->maxval; + + return 0; +}